The spatial expression pattern of antimicrobial peptides across the healthy bovine udder.

Antimicrobial peptides are key molecules in local host defense. With the aim to better understand the possible involvement of these peptides in the prevention of bovine mastitis, we determined, for the first time to our knowledge, the spatial pattern of constitutive expression of 5 bovine beta-defensins and bovine psoriasin (S100A7) across 5 localizations of the bovine mammary gland applying a quantitative real-time PCR approach. We observed 3 different expression patterns in the healthy udder: 1) constitutive expression of the lingual and tracheal antimicrobial peptides (LAP and TAP), as well that of bovine neutrophil beta-defensins 4 and 10 (BNBD4 and BNBD10), is essentially restricted to the mammary lymph node; 2) bovine beta-defensin 1 (DEFB1) is mainly expressed in the cisternal epithelium and the Rosette of Fürstenberg; 3) strong constitutive mRNA expression of the calcium-binding protein S100A7, which is also known as psoriasin and which has been reported to be highly active against Escherichia coli, was detected in the streak canal. These results indicate a crucial role of S100A7 in the early-stage prevention of coliform mastitis, and the analyzed beta-defensins might be regarded as inducible weapons against already invading pathogens.